If you have the bootloader unlocked, you should be able to get TWRP recovery flashed over in fastboot. I think you can do this with the all in one. Once you have that, boot into Recovery, hit the MOUNT button, plug into a PC, copy over whatever rom, then flash it.
You will probably have to achieve S-OFF or you will have to flash over the boot.img of every ROM you want to use. This first time, you will also have to extract that from the rom.zip file and flash it with fastboot. Once you do it that way the first time, you can install the flashgui application and use that to do it in the future (need root, so).
I think your next goal should be getting TWRP on there, a copy of the rom,zip file, and then achieve S-OFF.
EDIT- Removed link to incorrect thread... if you have INTL version, must use that.
This was not trivial, but if you can get this done, it will make your life easier in the long run. Otherwise, you need to do the flashing of the boot.img noted above.